1. Field of the Invention
This invention relates to the manufacture of filters, and more particularly to the manufacture of filters having molded plastic end caps.
2. Description of the Prior Art
Filters, such as fluid filters for gases and liquids used for motors, carburetors, compressors and other devices, are commonly formed of filter media or a filter element with top and bottom end caps formed on each end of the filter element. The end caps are usually molded in place by introducing plastic resin into the mold and positioning the filter element in a mold and allowing the resin to harden. When the filter element is positioned in the mold, the bottom end of the filter element rests on the upper surface of the interior of the mold.
In order to provide for sufficient plastic material between the end of the filter element and the exterior surface of the end cap, the interior surface of the mold has usually been provided with at least one ridge upon which the bottom end of the filter element rests. If the interior surface of the mold were flat, there would be very little if any plastic between the end of the filter element and the exterior surface of the end cap, and, as a result, the end of the filter element would be exposed and fluid could leak through end cap at this location. The ridges allow the end of the filter element to be raised above the remaining surface of the mold so that sufficient plastic is present between the end of the filter element and the exterior surface of the end cap when the end cap is formed. However, even when ridges are used, the end of the filter element is still exposed to the exterior of the end caps along these ridges, creating locations in which there is little or no resin material covering the end of the filter element, and the possibility still exists that the end caps could allow leakage of fluid at these locations.